Manufacture of fluosulfonic acid



NOV' 18 1947- R. sTEPHENsoN ET Al. 2,430,963

- MANUFACTURE OF FLUGSULFO-NIC ACID Filed NOY. 27, 1944 www Patented Nov. 18, 1947 UNITED STATES PATENTu OFFICE` Richard Stephenson, Long IslandCty, N..Y., and

William E. Watson, West Orange,V N; J., as'- signors to General Ghemical- Company, New- York, N. Y., a corporation-of New Yorkv Application November 27, 1944, SerialN/o.,565,294A

(Cl. .Z3- 1139i 2 Claims; l

This invention is directed to manufacture of fluosulionic acid (I-ISOaF), particularly iiuosulionic acidcontaining no dissolved HFand preferably to production of substantially pure fluo- -suli'onic acid containing no dissolved HF or S03- Fluosulfonio acid may be made by effecting combination of hydrogen fluoride and sulfur trioxide. rPheforms oi hydrogen fluoride and sulfur trioXi-de most readilyA available commercially are. as gases, such as the HF gasproduced by reaction of iiuorspar and sulfuric acid, and the. S03 gas formed by catalytic oxidation of SO2 to S03. During recent attempts' to develop proces-ses` for making fluosulfonic acid by gas-in-liquid absorption procedures commonly used in the chemical arts, itv was found markedly difficult to make a l'uosulionic acidproduct which does not contain` either anv` excess` of I-IF or an excess of' S03, the chiefy reasons being the substantial' solubility of. both I-I'F and S03 in fluosulfonic acid, fluctuations of the HE and/or S03 contents oi commercial gases, andthe mechanical diiicultiesencountered` in satisfactorily regulating the end point of. re.- action of a gas-liquid contacting operation. in which one or more of the reactants is. soluble inl the reaction product. Because of these factors, agi-'ven apparatus unit during one time interval formed a iiuosulfonic acid product containing an excessoiand during another interval a prod-- uct containing an excess of S03. Variability of the reaction has been such that, it. has been practically impossible to make products of consistent. composition.

This invention aims to provide, a process by which if' desired, substantially pure fluosulfonic acid' containing, substantially no dissolved HF or S03 maybe made without the use of procedural steps which are unreliable anddiicult to control.

The accompanying drawing shows diagrammatically apparatus inwhich a preierredembodimentof the process ofthe present invention may be carried out.

On the drawing, IU indicates a source of HF gas which may be made in any suitable manner. For example, one such gas is a crude HF gas formed by reaction of sulfuric acid and iiuorspar as known. in the art relating to the manufacture oi aqueous hydroiiuoric acid. Typical gases of thisnature may contain, by volume, from 40-80% HE, Zei-5%. Sim, a smallV amount ot SO2, and Water vapor depending uponthe'moisture content of the" iiuor-spar and the strength of the acid used in the? fluorspar-sulfuric aci'dreaction zone. Since water' and uosu'lfonic acidjreact to form I-IF and'HzSOr, in thet present, procesa, it is preferred toY utilize substantially anhydrous HF gases which, if"y desired, may be made by drying crudel Wet I-IF-gasf in any suitable way. Alternatively; hydrogen fluoride gas containing substantially no Water" may be produced by utilizing in a iiuorspa-resulfurie acid reaction zone a suiicient quantityfof" oleurnV of' strengthA and amount sufficient to' formv H2SO4 with all H2O brought into the sys tem, i. e. as moisture in the fiuorspa-r or aslwater" content of any sulfuric acid used whichI may be of strength less than 1'00 1`nl the practice of the present invention, the I-IFgas, at approximately room temperature, is' fedinto contact with uosulfonic acid" in any" suitable gas-liquor contacting apparatus. Thus, the cool crude I-IFr gas maybe introduced into the' bottom of an absorption tower I'l into the topV of which substantially pure fluosulfbni'c acid` is fed bymeans or a spray distributor |`2fandipif`pe I3" connected' to tank I4. The absorbin-gtowerl may be unobstructed or packed, and ifi desiredfa pluralityy of: towers connected in series maya be used; and absorption carried out on the counter# current principle:

Temperature conditions maintained duringthe contacting operation may be anything-f such` as to holdthey partial pressure of HF over theuosull' ionic acid in the absorbing zone to a point' less than the partial pressure oi HF in the incoming crude HF gas stream. Preferably, temperatures*y in the absorbing Zone are maintained"I in the neighborhood of 30 C. and ordinarily notl higher than 40 C.. Absorption of HF by the uosulfonic aciddevelopsA some heat andthe resultingltemperatureincrease maybe ofsetby adequatel coolingof the fluosulfonic acid during absorption or prior to introduction of the uosulfonic acid into the tower. The absorption operation isprefenf ably counter-current', and the quantity of'fiuo.- sul'fonic acid fed into the tower and rates'of flow of gas and liquor are controlled so as to provide iorsubstantially complete absorption of HFv out of the gas stream. Depending upon the particu lar designof tower Il, cooling facilities, and HET strength of incoming gra-s,` thequanti-tyoF fluo--y 3 sulfonic acid charged into the top of the tower may be regulated so that the HSO3F liquid effluent of the tower contains from say 3 to 50% by weight of dissolved HF. Under the absorbing temperatures and conditions indicated, solubility of SiF4 in fluosulfonic acid is substantially nil and, if present in the incoming gas, SiF4 and other constituents such as S02, C02 and air exit the top of the tower and are discharged from the system as tail gas. Assuming use of a substantially dry HF gas and a substantially pure HS03F absorbent, there is produced an absorbing tower effluent liquor consisting of HSOaF and dissolved HF in the variable amounts indicated, and such liquor is run thru pipes I6 and II into tank I8, the valve 2| in pipe 22 being closed.

In accordance with the preferred embodiment of this invention, substantially pure'fluosulfonic acid is made by incorporating, Awith a substanacid and dissolved HF, a substantially anhydrous Y liquid mixture consisting of fluosulfonic acid and Since in the practice of this emdissolved S03. bodiment, all of theS03 constituent of the final HS03F product is brought into the system as the S03 constituent of the HS03F-S03 mixture, it is preferred to use a mixture which is high in S03, for example, a mixture consisting of fluosulfonic acid and not less than v50% by. weight (of the mixture) of dissolved S03. Because of high solubility of S03 in uosulfonic acid, it is possible to make and use in the instant process, a mixture containing by weight as much as 70% dissolved S03, the balance being HS03F.

An HS03F-S03 mixture of the kind described may be made conveniently by distilling commercial oleum in a still in such a way as to form a substantially 100% S03 gas, and dissolving the S03 in HSOall. For this purpose, substantially pure fluosulfonic acid is drawn out of tank I4 and run thru pipe 23 and spray head 30 into the top of tower 2l, while the S03is fed into the bottom of the tower by pipe 3|. In tower 21, rates of introduction of uosulfonic acid and S03 gas and cooling, by external or other suitable means, of the counter-current contacting operation are regulated so as to effect substantially complete absorption of S03 and form a substantially anhydrous liquid tower eluent which is luosulfonic acid containing dissolved S03 in amount suitable for the particular operation at hand. S03 absorption temperatures should be held preferably at C. or less. Thus, the liquor collected in tank 32 may contain anywhere-from say 10 to 70% by weight of dissolved S03. Tower 2l may be replaced by a simple externally or internally cooled tank providedV with means to bubble sulfur trioxide into a body of uosulfonic acid. Alternatively, the IIS03FS03 mixture may be made by contacting fluosulfonic acid with S03 gas produced by catalytic oxidation of S02 to S03. In this instance, a plurality of contact towers connected in series and provided with suitable coolers and liquor recirculating equipment may be used. The fluosulfonic acid is run int-o the last tower of the series, and the S03 gas into the rst, absorption being carried out on the counter-current principle, and the number ofV towers being dependent upon good clean-up of S03 and the desired dissolved S03 strength of the HS03F-S03 mixture to be formed.

When an adequate amount of HS03F-HE liquor produced in tower II has been run into tank I8, valve I9 is closed and valve 2I is opened to collect the continuing production of tower I I in tank 34.

Analyses of the liquors in tanks I8 and 32 are made, and depending upon such analyses, there is run into tank I8, thru pipe and valves 36 and 31, such an amount of the HS03F-S03 mixture from tank 32 as to provide, in the resulting composite liquor in tank I8, S03 in quantity preferably substantially equal to the stoichiometric amount required to react with all of the dissolved HF present in tank I8 to form lluosulfonic acid. For example, if the liquor in tank I8 analyzes by weight HS03F and 10% HF, and the mixture in tank 32 analyzes by weight 50% HS03F and 50% S03, to each pound of liquor in tank I8 there would be added 0.8 pound of the HSO3F-S03 mixture from tank 32. During the mixing operation, the liquor in tank I8 is kept at temperature preferably less than about C. to prevent stripping out of HF and vaporization of any of the liquid. The substantially pure fluosulfonic acid thus formed in tank I8 is run into the intermediate collecting tank I4 from which the required amounts of fluosulfonic acid are withdrawn, further cooled if necessary, and recirculated by pipes I3 and 29 over towers II and 21. Production of a substantially pure product in tank 34 is effected in the same manner as already described in connection with tank I8, and the make of the process is run out of tank I4 into product storage tank 40.

In some industrial processes, the presence of relatively small amounts of sulfuric acid in fluosulfonic acid is not objectionable and is regarded as a diluent. Thus, in all cases the HF gas from source I0 need not be substantially anhydrous but may contain water in amount such that the quantity of sulfuric acid (formed by reaction of H2O and I-ISO3F) in the final product is not abovev the permissible value for the circumstances at hand.

In certain other processes in which rluosulfonic acid is employed as a reactant, the presence of relatively small amounts of dissolved S03 in the iiuosulfonic acid is not objectionable. Accordingly, while in the practice of the present invention the quantity of available S03 brought into the process is proportioned so as to provide for the substantially complete elimination of dissolved I-IE, the amount of S03 brought into the instant process as in tanks I8 and 34 may be in appreciable excess of that required to get rid of the dissolved HF.

By forming a luosulfonic acid liquor containing a substantial amount of dissolved HF, and bringing the S03 into the process in the form of the liquid mixture described, the invention allords the substantial operating advantage of making it possible to accurately proportion the total amounts of HF and S03 in the system, and accom. plish this end by use of a material which, in spite of its permissibly very high S03 content is nonfreezing and remains in uid, readily handleable condition at room temperature. Accordingly, the invention facilitates production Of substantially pure product without the necessity of becoming involved in all the operating diii'iculties entailed in the determination of the proper end point of a gas-liquid contacting operation.

What is claimed as the invention is:

1. The process for making fluosulfonic acid which comprises forming in one receptacle a uosulfonic acid liquor containing dissolved HF, and incorporating with said liquor a liquid mixture formed in another receptacle and comprising lluosulfonic acid containing dissolved S03, the amount of said mixture being such as to in- 5 troduce, into the resulting liquid, S03 in quantity at least equal to the stoichiometric amount required to react With HF present to form fluosulfonic acid.

2. The process for making substantially pure 5 fluosulfonic acid which comprises forming in one receptacle a substantially anhydrous liquor consisting of uosulfonic acid and dissolved HF, and incorporating with said liquor a substantially anhydrous liquid mixture formed in another recepl tacle and consisting of fluosulfonic acid and dissolved S03, the amount of said mixture being such as to introduce, into the resulting liquid, S03

REFERENCES CITED The following references are of record in the 0 le of this patent:

FOREIGN PATENTS Country Date Great Britain 1910 Number 

